1. Field of the Invention
This invention relates to an image processing apparatus and image-processing method of compensating the shake of an image obtained by a camera mounted on a mobile object represented by vehicles, such as a car.
2. Description of the Related Art
Generally, movement of a mobile object generates a shake in a video image by the unevenness of the ground, or steering of the mobile object.
In the device which detects an obstacle by analyzing the motion vector (optical flow) of each point of the video image, using the video stream inputted from a TV camera, the camera shake becomes the cause of detecting the obstacle accidentally. Therefore, it is necessary to compensate in advance the shake of a video image caused by the shake of the TV camera. In order to compensate the shake of the video image, the TV camera shake must be detected. In the method of detecting the camera shake there are a method that uses additional devices, such as an angular-velocity sensor, and a method that measures the variation in the obtained image. Moreover, in a method of compensating the image shake there are a method that compensates the image shake optically, and a method that compensates the image shake in software. The optical compensation method compensates the image shake optically by mounting an actuator, a variangle prism, etc. in TV camera. The software compensation method compensates the shake by transforming the video image based on an amount of shake, and extracting a part of the video image.
In a case where an obstacle is detected by the TV camera mounted on the mobile object, the method which compensates the shake in software is advantageous in the following points. That is, there is no fall of the durability because of a movable mechanism. Since devices other than the TV camera are unnecessary, cost can be reduced.
Moreover, when the mobile object moves at high speed, the video image obtained by the TV camera mounted on the mobile object changes violently in almost all the regions in a screen. For that reason, there is a problem that it does not know whether the motion is caused by the shake or it arises from translation of the mobile object even if the motion vector of the region in the video image is detected based on such a video image.